Method of handling, conditioning and processing steel slags

ABSTRACT

An apparatus and method for separating metal rich slag and metal poor slag are provided. A slag pot is allowed to partially cool, agglomerating the metal in the pot. A portion of the partially cooled slag is poured down a first ramp, providing a metal poor slag. Optionally, this slag is cooled with water. The remaining slag in the slag pot is poured down a subsequent ramp, resulting in the separation of a metal rich slag. Optionally, the latter step is repeated with any slag remaining in the slag pot.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of co-pending provisional patentapplication Ser. No. 60/833,680 entitled “Method of Handling,Conditioning, and Processing Steel Slags,” filed on Jul. 27, 2006, theentire disclosure of which is incorporated by reference herein.

FIELD OF THE INVENTION

The present invention is directed toward the handling of slag generatedin the process of steel melting, from the EAF (Electric Arc Furnace),AOD (Argon-Oxygen Decarburization) or converters' tap-hole, theconditioning of the slag to recover as much entrenched metal aspossible, and generating an aggregate usable for civil construction,road building, etc. More specifically, the present invention covers thetilting, the cooling, the crushing and sizing of the slag, and also theprocessing of the slag to recover the metal in the slag.

BACKGROUND OF THE INVENTION

Steel production generates a by-product called slag. This by-product isgenerally formed by the additives added during the steel meltingprocess, such lime, flux, an others, and also by the impurities from theraw materials used to make the steel. A limited quantity of metal isalso entrenched in the slag.

In molten slag, the metal is typically in the form of small droplets.During the cooling of the slag, and depending upon the method of coolingused, the metal droplets tend to agglomerate and form bigger pieces ofmetal. As the metal density of these pieces becomes higher than thedensity of the molten slag, the metal tends to sink to the bottom of theslag pot.

Usually the slag is removed from the furnace by drilling a tap hole intothe furnace and allowing the molten slag to drain from the furnace intoa slag pot placed in front of the furnace through the tap hole. Once thetapping operation is completed, the slag pot is removed from themelt-shop and carried either on railroad cars, slag-pot carriers orspecially designed vehicles to a slag dumping station. Differenttechniques are used to remove the slag from the slag pot. In some cases,the slag pot is left to cool down a certain period of time (typicallyfrom a few hours to a few days), or put into “pool,” or the molten slagmay be dumped into bunkers or a slag pit. In this later approach ofdumping the molten slag into a bunker or slag pit, the slag might beleft to cool, once again from a few hours to a few days. Once cooled,the slag is typically removed by a front-end loader or excavator andhauled away for further processing.

The cooled slag is generally processed through different stages, such asbeing crushed, grinded and/or handpicked to recover the metal present inthe slag. Handpicking the metal is a procedure generally utilized forthe coarser slag. The finer slag is processed such that the recovery ofsmall pieces of metal is possible.

Once again, different techniques exist to process the finer fraction ofslag. Some techniques grind the slag very fine (e.g., 100% minus 250microns). This technique allows for recovery of more than 98% of themetal from the slag. The remaining aggregate is a fine powder and fewapplications are available to recycle it. Other techniques use eithermagnetic or density separation. This will maintain the physicalproperties of the slag but the rate of recovery is low, typically at 50%to 65% metal recovery.

There is a growing trend in the steel industry to produce from slag anaggregate which is harmless for both the environment and human-beings,and that can also be used for construction works and other applications.This would reduce the amount of slag stockpiled and also reduce the riskof further environmental problems.

BRIEF DESCRIPTION OF THE INVENTION

An apparatus and method for separating metal rich slag and metal poorslag are provided. A slag pot is allowed to partially cool,agglomerating the metal in the pot. A portion of the partially cooledslag is poured down a first ramp, providing a metal poor slag.Optionally, this slag is cooled with water. The remaining slag in theslag pot is poured down a subsequent ramp, resulting in the separationof a metal rich slag. Optionally, the latter step is repeated with anyslag remaining in the slag pot.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a top view of part of an exemplary apparatus for quickquenching and separating liquid slag. In the present invention, two ormore of these apparatuses would be in close proximity to the slag pot,allowing the contents of the slag pot to be poured down each apparatusin turn, creating increasingly metal-rich slags; and

FIG. 2 is a cross-sectional view of the apparatus shown in FIG. 1 takenalong line A-A.

DESCRIPTION OF THE INVENTION

The present invention is based on tapping the slag from the furnace intoa slag pot. The slag pot is hauled to a dumping station. The slag mustbe liquid and kept hot (i.e., molten) and the viscosity of the slagshould be between determined parameters, as will be discussed hereafter.Additives, such as borax, etc., can be added to the slag pot to increasethe heat and the viscosity of the slag. The time between the tapping ofthe slag from the furnace and transporting the molten slag to thedumping station is typically less than an hour, but a minimum period oftime is required to allow the metal droplets to agglomerate and sink.During that time period, the metal droplets present in the slag willhave time to sink to the bottom of the slag pot, therefore agglomeratingand creating bigger pieces of metal which will help in the metal removalprocess.

The slag pot is then presented to the dumping station. The dumpingstation should house at least two or more ramps, which may each be asshown in FIG. 1 and described herein. At the end of each ramp, ahorizontal elevated platform allows the vehicle with the slag pot toposition itself for tilting. The elevated platform may be, for example15-18 feet high. However, other heights are contemplated, as discussedbelow. The platforms may be of different heights. The slag pot will betilted at the end of the platform onto a cooling bed consisting of aramp having a predetermined angle of inclination (i.e., slope). The rampmay be oriented at one continuous angle, or may be arranged such that ithas various different angles as the ramp extends from the elevatedplatform to its end. Typically, the more molten the liquid slag is, theless of an angle the ramp should have to prevent the liquid slag fromrunning down ramp too quickly. Thus, depending on the angle of the ramp,the viscosity of the molten slag should be adjusted so that there issufficient time for it to cool and harden before reaching the end of theramp.

The ramp will also have a minimum length to allow the slag to run downthe ramp and cool before reaching the end. One length contemplated is 50feet, but other lengths may be used and will generally depend on theviscosity and amount of liquid slag being cooled as well as the angle ofthe ramp. The viscosity of the slag should be such that it will coolbefore reaching the end of the ramp. The ramp should consist of steelplates with a specified thickness to avoid deformation caused by thehigh temperature of the liquid slag.

Spraying bars located on both sides of the ramp will spray water ontothe liquid slag as it is dumped onto the ramp. The water helps to coolthe slag as it runs down the ramp. Applying the quantity of water for alimited period of time is crucial to modify the physical characteristicsexpected (i.e., turn the liquid slag into a crystalline form) and thequality of the slag. In one form of the invention, it has beendetermined that it takes approximately 8 minutes for the liquid slag tocool and turn into a crystalline form as it is being quenched withwater. During this 8 minute period, water is constantly applied to theliquid slag. However, other application periods are contemplated. Forexample, water may be applied for less than 8 minutes, for 4 minutes, 5minutes, 6 minutes, 7 minutes, 9 minutes, 10 minutes, or greater than 10minutes.

In accordance with the present invention, the tilting of the slag potcarrier is controlled. In one embodiment, a maximum of 75% to 80% of theslag will be tilted (i.e., dumped onto the ramp) in the first step. Theamount of slag tilted during the first step may be, for example, but isnot limited to, between 70% and 85%, between 65% and 90%, or between 70%and 80%. The remaining slag (or an amount of the remaining slag, if morethan two ramps are to be used) is tilted onto a separate ramp bunkerlocated beside the first ramp. This second tilting may be processed inthe same way as previously described for the first tilting, namely,applying water to the slag as it runs down the ramp to cool the slag andturn it into a crystalline form.

The second tilting typically accounts for 20% to 25% of the slag andwill generally include 85% to 95% of the metal in the slag (again, otherpercentages are contemplated, and where two ramps are used the amount ofslag in the second tilting will account for the balance of the moltenslag left following the first tilting). Thus, the metal content in thefirst tilting should consist of between 5% to 15% of the metal in theslag. One skilled in the art will readily understand that the metalcontent percentages will very depending upon the amount of metal thatagglomerates and sinks to the bottom of the slag pot. Thus, the slag potmust be given a sufficient minimum period of time to allow the majorityof the metal present to agglomerate and sink to the bottom of the slagpot. The present invention contemplates, however, that the first tiltingwill have a decisively lower metal content that the second tilting.

The slag tilt in the first instance, which is referred to herein as the“metal poor slag,” is removed immediately after tilting/cooling andstockpiled. In a preferred embodiment, the metal poor slag is dumped ina building or under a roof.

The quenched slag is a porous, light greenish colored aggregate. Forslag containing chrome (such as stainless steel slag), by shortening thecooling phase the process reduces the phase chrome hexavalent formationand therefore reduces environmental problems involved with processingstainless steel slag in particular.

The metal poor slag is later processed in a crushing-screening plant andreduced to a desired particle size of approximately 0-20 mm or 0-32 mm,or other sizes, according to various market requirements. The metal poorslag is first screened to remove the larger pieces of metal. During thecrushing and sizing phase, a high-intensity magnet recovers freemetallic particles in the slag and also mixed particles (pieces of metalwith slag attached). This operation further reduces the metal content inthe metal poor slag.

The slag tilt in the second instance is referred to herein as the “metalrich slag.” After cooling, the metal rich slag is removed from thedumping area and may be processed through a wet-dressing plant. Thewet-dressing plant generally consists of grinders, such as rod mills andball mills, screw classifiers and high intensity magnet(s). The metalrich slag is typically ground to a size that is minus 1 mm. At the endof the process, a metallic concentrate is generated, usually in thefraction of 0 to 6 mm. This concentrate is typically between 93% and 96%metallic, though it may vary depending on the initial metal content ofthe slag. Additionally, the mixed particles recovered during thecrushing and screening of the metal poor slag are also processed throughthe wet-dressing plant to increase the rate of recovery of the metal inthe slag.

The final aggregate produced by the above-described process typically is100% minus 250 microns in size and contains less than 0.020% of metal.As a result of the low metal content, the aggregate is generallyenvironmentally safe.

It should be noted that although the handling of steel slag is describedin various embodiments reported herein, the handling of other moltenmetal slags may also benefit from the processes and apparatuses reportedherein.

Those skilled in the art will recognize that the operation of the slagpot may be controlled by computer, which may allocate slag dumpsaccording to factors including the weight of the slag pot, calculationof slag density and composition, and the like.

A third aspect of the present invention is the contribution to a betterenvironment. The metal poor slag which represents a large portion of thetotal slag generated by the mill can be marketed as aggregate for civilconstruction applications, and because of its special characteristics,such as porosity and stability, it is a perfect material for insulation,drainage material, and the like. The processed slag aggregate can beused as is or with a binding agent, such as cement, bituminous cement orvarious other kinds of binder.

The fine fraction of the processed slag can be utilized in manydifferent applications, such as, but not limited to, as engineeringmaterial, light artificial aggregate, in the production of concretebricks, pavers, pre-manufactured concrete pieces or structures, and soon.

One ramp apparatus that may be used in embodiments of the invention isdescribed hereafter. It should be understood that multiple ramps shouldbe present, to allow the metal rich slag and metal poor slag to beseparated. If only two ramps are present, multiple slag pots may beemptied on each ramp before the slag is removed; this would allow all ofthe metal-rich slag from multiple slag pots to be accumulated on asingle ramp, and all of the metal poor slag from those pots to beaccumulated on another ramp. It should further be understood that rangesand parameters given in the description of the ramps are exemplary andshould be construed as alternatives to other ranges and parameters inthis application.

Referring to FIGS. 1-2, an exemplary apparatus for quick quenchingliquid, or molten, slag is illustrated, shown generally at 10. Theapparatus 10 generally includes a bay area 12 and a trough area 14. Theliquid slag is cooled in the bay area 12 by the application of waterunder pressure, such that the cooled slag remains in the bay area 12.The trough area 14 receives the water running from the bay area 12 anddirects it to a sedimentation pond 16, where the water can be recycledfor further quenching or other applications.

The bay area 12 generally includes a plurality of steel slabs 18 whichare installed side by side to form a flat surface. Liquid slag (notshown) is poured onto the steel slabs 18 for cooling, and thus the steelslabs 18 need to be able to withstand the high temperature of the liquidslag. The steel slabs 18 are oriented generally at an angle, with thelow end 19 adjacent the trough area 14, such that the liquid slag andthe water applied to the liquid slag run down the steel slabs 18 towardthe trough area 14. In the exemplary form of FIGS. 1 and 2, the bay area12 is approximately 50 feet long and the trough area 14 is approximately80 feet long. However, other lengths for these areas are contemplated.

A dumping platform 20 is provided at the high end 21 of the steel slabs18. The dumping platform 20 is typically made of concrete, and may beapproximately 4-10 feet high. However, other heights are contemplated.Liquid slag (not shown) is transported to the dumping platform 20 viatrucks, slag pot carriers or other appropriate vehicles and poured ontothe steel slabs 18 of the bay area 12. The poured liquid slag willspread out across the steel slabs 18 and run down toward the trough area14 due to the angle of inclination of the steel slabs 18. To prevent theliquid slag from running off of the sides of the steel slabs 18,vertically oriented steel plates 22 are provided on opposite sides ofthe surface formed by the steel slabs 18. In the exemplary form of FIGS.1 and 2, the steel slabs 18 have a width of approximately 24 feetacross, which is typically sufficient to accommodate the poured liquidslag without resulting in excess slag at the edges. However, otherwidths for the steel slabs 18 are contemplated.

In one form, the steel slabs 18 have two different angles of inclinationextending from the dumping platform 20 to the trough area 14. A firstarea, shown generally at 24, is adjacent the dumping platform 20 andincludes a first angle of inclination, while a second area, showngenerally at 26, extends to the trough area 14 and includes a secondangle of inclination. As shown in FIG. 2, the first angle of inclinationof the first area 24 is greater than the second angle of inclination ofthe second area 26. In this manner, liquid slag poured onto the steelslabs 18 is poured from the dumping platform 20 onto the first area 24.The liquid slag will begin to run toward the trough area 14 and spreadgenerally evenly and thinly across the steel slabs 18. Once the liquidslag hits the second area 26, which is oriented at less of an angle, itwill tend to run slower. The angle(s) of inclination of the steel slabs18 should be chosen so that the liquid slag will stop running down thesteel slabs 18 before it reaches the trough area 14. This aids inremoving the slag since all of the cooled and crystalline slag willremain on the bay area 12, and also helps alleviate a hazardouscondition since if the liquid slag would trap any water remaining in thetrough area an explosion may occur.

In one embodiment, as shown FIG. 2, the angle of inclination of thefirst area 24 is approximately 17°, while the angle of inclination ofthe second area 26 is approximately 5°. However, these angles are forillustrative purposes only, and other angles of inclination arecontemplated without departing from the spirit and scope of the presentinvention. For example, the steel slabs 18 may be oriented at onecontinuous angle, or may be arranged such that they have variousdifferent angles as they extend from the dumping platform 20 to thetrough area 14. In one exemplary form of the present invention, theangle of inclination of the steel slabs 18 will tend to decrease as onemoves away from the dumping platform 20 toward the trough area 14.However, any configuration of angles of inclination of the steel slabs18 may be implemented without departing from the spirit and scope of thepresent invention.

The only requirement is that the liquid slag spread out across the steelslabs 18 (a thin layer of liquid slag will cool more quickly) and rundown toward the trough area 14, stopping before reaching the trough area14. The angle(s) of inclination of the steel slabs 18 (i.e., bay area12) will depend on various factors, such as, but not limited to, thetemperature and viscosity of the slag, as well as the amount of slagbeing quenched. Generally, a higher temperature slag will be moreviscous than a lower temperature slag. Typically, the more molten (i.e.,more viscous) the liquid slag is the less of an angle the steel slabs 18should have to prevent the liquid slag from running down the steel slabs18 too quickly and possibly running off of the steel slabs 18 and intothe trough area 14. The goal is to have the slag spread evenly andthinly across the steel slabs 18 and stop before reaching the end of thesteel slabs 18. The steel slabs 18 (i.e., bay area 12) should be madelong enough so that the liquid slag stops running down the steel slabs18 before reaching the trough area 14. As shown in FIG. 2, in one form,the bay area 12 is approximately 50 feet long. However, others lengthsare contemplated and generally will depend on the temperature, viscosityand amount of liquid slag being cooled.

Once the liquid slag is poured onto the bay area 12 and spreads outacross the surface formed by the steel slabs 18, it is hit with lowpressure cold water via a water supply system 28. The water cools theliquid slag almost instantly (a thin layer of liquid slag will coolquicker than a thicker layer). As the liquid slag is quickly cooled, orquenched, using the low pressure water, it turns into a crystalline, orglass-like, form. Since the cooled, crystalline slag should be presenton the steel slabs 18 on the bay area 12, it can be easily removed usinga front-end loader or other similar vehicle.

As the slag hardens and turns into a granulate form, some dust may begenerated. The water being applied to the liquid slag helps to eliminatedust from being transported into the air. Additionally, the spray barsand nozzles, which make up the water supply system 28, may be designedto contain the steam generated as the slag cools within the quenchingarea. For example, the spray nozzles used may apply a cone-like spray ofwater onto the liquid slag. Typically, the spray bars and nozzles willbe positioned to spray water over the entire surface of the steel slabs18, and thus over all of the liquid slag being cooled. The spray formsan umbrella over the slag trapping any steam generated. This trappedsteam will cool and turn back into water. As a result, approximately25-30% less steam may be generated in cooling the liquid slag. However,the spray bars and nozzles may also be configured such that no steam iscontained during the quenching process. Additionally, the nozzles can beinstalled along each side of the steel slabs 18 spraying water towardthe liquid slag.

Typically, the water applied to the liquid slag will be uniform inpressure and application. The present invention contemplates utilizing alow pressure water system (e.g., between approximately 10-30 psi) toapply a high volume of water (e.g., between approximately 800-2000gallons/minute) in order to appropriately quench the liquid slag. Theamount of water needed to thoroughly cool the liquid slag will depend ona number of factors, such as, but not limited to, the temperature,viscosity and amount of liquid slag being cooled (typically thetemperature of the slag will decrease from the time it is tapped untilthe time it is brought to the platform to be quenched), the angle of thesteel slabs 18, the thickness of the liquid slag as it runs down thesteel slabs 18, the temperature of the water (the water used to cool theslag may become warmer if the water is being recycled for use), meltshop practices which may affect the viscosity of the slag, etc.

In order to determine the appropriate amount of water to use to cool theliquid slag, it is contemplated to first perform a “test run” of sortsand cool a batch of liquid slag applying water at a rate ofapproximately 1200 gallons/minute for 10 minutes. The slag is thenchecked to determine if it has cooled all the way through andadjustments can be made to the amount of water applied and also to theangle of the steel slabs to determine optimum parameters for cooling theliquid slag. If the bottom of the slag next to the steel slabs 18 doesnot cool and turn crystalline, it will generally turn into a powderyform which is undesirable.

As the liquid slag cools and turns into a granulate form, the waterwhich is applied to the liquid slag continues to run down the steelslabs 18 and is received at the trough area 14. Berms 30 are formed oneither side of the trough area 14 and channel the water as it flows downthe trough area 14 (see FIG. 1). The berms 30 may be formed of anymaterial and, in one form, are formed of slag or fine aggregate or othersimilar material. The trough area may be virtually any length and, inone form as shown in FIG. 2, is 80 feet in length.

The sedimentation pond 16 is provided at an end of the trough area 14and receives the water flowing down the trough area 14. A water drain ora sump pump 32 is provided which drains or pumps the water from thesedimentation pond 16, and may direct the water to an area where it canbe recycled for further quenching or other applications. Typically, thedrain/pump 32 will include a cover to prevent large debris from enteringthe drain/pump. It has been found that the water run off from theabove-described quenching process is mostly clear and free of fineparticles and, thus, the water may be recycled through a closed loopsystem and reused for further quenching with minimal mechanical and/orchemical treatment. The water from the quenched slag can also bedirected to a unique pond or basin system where the water can beimmediately pumped to the quenching spray bars. Depending on thefrequency and volume of liquid slag that is being cooled down, a largerpond or basin system that overflows one after the other or a coolingtower can be used to help the water cool down before being re-used tohelp increase the effectiveness of the water.

After the liquid slag is cooled, it remains on the steel slabs 18. Aspreviously mentioned, in order for the cooled slag to be easily removed,the length of the bay area 12 should be such that the slag stops movingbefore reaching the low end 19 of the bay area 12. A second batch ofliquid slag may be poured on top of the already cooled slag, andquenched with low pressure cold water in the manner previouslydescribed. In this case, the duration of quenching will be set to ensurethat enough heat remains in the slag and steel slabs 18 to bum off allremaining water and moisture before dumping another layer of liquid slagover the previous one. In one form, it is contemplated that the cooledslag and steel slabs 18 remain at a temperature of approximately200-250° F. to bum off any excess water or moisture remaining beforedumping an additional batch of slag on top for cooling. However, othertemperatures may be utilized without departing from the spirit and scopeof the present invention.

Cooling a number of batches of liquid slag on top of each other helps toreduce material handling costs, and a plurality of batches of liquidslag may be cooled on top of each other. Once a desired amount of slaghas been cooled, it is removed from the steel slabs 18. A front-endloader, or other similar vehicle, accesses the trough area 14 via aloader access ramp 34. The front-end loader will drive up the trougharea 14 and remove the cooled liquid slag from the steel slabs 18. Thecooled liquid slag, which is in a granulated, or crystalline, form, maybe used for a variety of purposes, including landfills, cementitiousapplications, or it may be further processed for other applications. Inits crystalline form, the cooled slag generally has high cementitiousand/or pozzolanic properties, making it particularly useful forcementitious applications.

As the water is sprayed onto the liquid slag, care is taken so that thewater is applied with a uniform pressure and application. Thus, thespray bars and nozzles of the water supply system 28 should be design touniformly spray the liquid slag with water at a constant pressure andvolume. Should water get under the hot liquid slag material, explosionsmay occur sending molten slag spraying into the air. Thus, care needs tobe taken, and the spray bars and nozzles of the water supply system 28designed, so that the low pressure water is applied uniformly over theliquid slag. While a preferred embodiment of the present inventioncontemplates spraying the liquid slag with a low pressure water, a highpressure water may also be used without departing from the spirit andscope of the present invention, as long as care is taken to not getwater under the liquid slag. For example, the pressure of the water maybe dictated by the specific nozzle design used.

It is imperative that the bay area 12 be totally clear of water, puddlesof water and moisture before dumping the liquid slag thereon or anexplosion may occur. Additionally, the trough area 14 should also befree of water or puddles of water in case the liquid slag runs off thebay area 12 and into the trough area 14.

The present invention has been described herein with reference tovarious ranges, which are exemplary only. One skilled in the art willunderstand that various modifications may be made to the inventivemethod and ranges without departing from the spirit and scope of thepresent invention.

1. An apparatus for separating metal rich slag from metal poor slag, comprising: at least two bay areas, each having an angled and generally flat surface provided between first and second ends, wherein the first end defines a high end and the second end defines a low end, such that liquid slag provided to a bay area adjacent to that bay area's first end will run down that bay area toward that bay area's second end; and a water supply system provided for the bay areas, the water supply system applying water to the liquid slag on each bay area such that the liquid slag cools and turns into a crystalline form.
 2. The apparatus of claim 1, further comprising a dumping platform provided adjacent the first end of the bay areas, wherein liquid slag is poured onto each bay area from the dumping platform.
 3. The apparatus of claim 2, wherein said dumping platform is configured to receive a slag pot.
 4. The apparatus of claim 3, wherein liquid slag is in said slag pot, and wherein said slag pot is configured to sequentially dump said liquid slag onto said bay areas.
 5. The apparatus of claim 5, wherein said slag pot is configured to sequentially dump predetermined amounts of liquid slag into each of said bay areas.
 6. The apparatus of claim 5, wherein there are two bay areas.
 7. A method of separating liquid slag into fractions of metal rich slag and metal poor slag, comprising the steps of: providing at least two bay areas, each having an angled and generally flat surface provided between first and second ends, wherein the first end defines a high end and the second end defines a low end; providing a slag pot containing liquid slag, wherein said liquid slag contains metal; pouring an amount of liquid slag onto the bay area adjacent the first end of a first bay, such that the liquid slag spreads out across the bay area surface and runs down the first bay area toward the second end; and applying water to the liquid slag on the first bay area such that the liquid slag cools and turns into a crystalline form, making a metal poor slag fraction; pouring the remaining slag on the remaining bay areas adjacent to the first end of each of said remaining bay areas, such that the liquid slag spreads out across the bay area surface and runs down each bay area toward the second end of each remaining bay area; and applying water to the liquid slag on the remaining bay areas such that the liquid slag cools and turns into a crystalline form, making one or more metal rich slag fractions.
 8. The method of claim 7, wherein there are two bay areas.
 9. The method of claim 8, wherein the first amount of slag poured to form the metal poor slag is between about 75% and 80% of the slag in the slag pot.
 10. The method of claim 9, wherein the metal rich slag crystallized in the second bay comprises about 85% to about 95% of the metal initially present in the liquid slag.
 11. The method of claim 7, further including the step of cooling said liquid slag prior to any pouring step.
 12. The method of claim 11, wherein said cooling step lasts between about 5 minutes to about 30 minutes. 